This invention relates to the field of electrically conductive fibers, especially antistatic fibers comprising polymeric materials, and a means for making same.
In many applications where fibrous materials are used, static electricity is often problematic. For example, in laybelt applications, where monofil fibers are often used, or in carpeting, where multiple yarns are frequently preferred, friction often produces static charges that interfere with the use or enjoyment of the material. Static electricity can cause a spark discharge of a static electrical charge that has built up, usually as a result of friction, on the surface of a non-conductive material. A material having a sufficient amount of electrical conductivity, i.e. low electrical resistivity, to dissipate an electrical charge without a spark discharge would not exhibit problematic static electricity.
U.S. Pat. No. 3,969,559 teaches a textile antistatic strand comprising a thermoplastic polymer in which carbon black is uniformly dispersed to provide conductivity. The antistatic strand is partially encapsulated by another, non-conductive, thermoplastic polymer constituent. The electrical conductivity decreases as the tenacity of the fiber increases with increased draw and hot roll temperature.
U.S. Pat. No. 4,185,137 teaches a conductive sheath/core heterofilament having a thermoplastic polymer core in which is dispersed a material selected from the group consisting of zinc oxide, cuprous iodide, colloidal silver, and colloidal graphite.
U.S. Pat. No. 4,255,487 teaches an electrically conductive textile fiber comprising a polymer substrate which contains finely divided electrically conductive particles in the annular region at the periphery of the fiber.
U.S. Pat. No. 4,610,925 teaches an antistatic hairbrush filament having a nylon or polyester core and a compatible polymeric sheath containing carbon.
U.S. Pat. No. 3,803,453 teaches a synthetic filament comprising a continuous nonconductive sheath of synthetic polymer surrounding a conductive polymeric core containing carbon.
Although it is known to make conductive or antistatic polymeric fibers by including conductive particles, when such fibers are drawn to increase the strength of the fiber or orient the polymer molecules the conductivity is significantly reduced or eliminated.